The objective of the proposed research is to the study of neuropeptide systems in the nervous systems of birds and reptiles using immunohistochemical techniques and conventional pathway tracing techniques. The nervous systems of birds and reptiles are fundamentally similar to those of mammals, but simpler in organization and may offer useful models for the further evaluation of the neural roles of the neuropeptides. The indirect immunofluorescence and immunoperoxidase bridge methods will be used to map the distribution of several major peptides shown by our preliminary research to be contained within avian and reptilian nervous system (substance P, the enkephalins, neurotensins and somatostatin). Additional immunohistochemical studies will examine avian and reptilian nervous system for the presence of further neuropeptides (vasoactive intestinal polypeptide, cholecystokinin, etc.). Detailed anatomical studies (using immunohistochemical techniques in conjunction with fiber transection and using conventional pathway tracing techniques) are planned of two major, possibly peptidergic, pathways in avian and reptilian brains: 1) a substance P pathway from basal ganglia to tegmentum, and 2) an enkephalinergic pathway from pretectum to tectum. Additional peptidergic pathways indicated by mapping studies will be examined via pathway tracing techniques and immunohistochemical techniques in conjunction with fiber transections. The goal of studies of peptidergic pathways will be to confirm the existence of such pathways and determine their precise origin, course and termination sites. Studies of neuropeptides in birds and reptiles may aid in the understanding of basic features of neuropeptide representation in the amniote nervous system. Such understanding may help in the evaluation of the proposed transmitter or modulator functions of the neuropeptides.